The growth of the open hearth or what is known as the Siemens-Martin
process of making steel, during the interval from 1869 to the present
time, has been no less remarkable than that of the Bessemer process;
for though it has not attained the enormous dimensions of the latter,
it has risen from smaller beginnings. Mr. Ramsbottom started a small
open-hearth plant at the Crewe Works of the London and North-Western
Railway, in 1868, for making railway tires, and the Landore Works were
begun by Sir W. Siemens in the same year. On the Continent there were
a few furnaces at the works of M. Emile Martin, at the Firming Works,
and at Le Creuzot. None of these works, I believe, possessed furnaces
before 1870, capable of containing more than four-ton charges,
ordinarily worked off twice in twenty-four hours. The ingots weighed
about 6 cwt., and the largest steel casting made by this process, of
which I can find any account, did not exceed 10 cwt. At the present
day, we have furnaces of a capacity of from 15 to 25 tons, and by
combining several furnaces, single ingots weighing from 120 to 125
tons have been produced at Le Creuzot. The world's production of
open-hearth steel ingots for ship and boiler plates, propeller shafts,
ordnance, wheels and axles, wire billets, armor plates, castings of
various kinds, and a multiplicity of other articles, cannot have been
less than from 800,000 to 850,000 tons in 1882.
The process itself has followed two somewhat dissimilar lines. In this
country, iron ores of a pure quality are dissolved in a bath of pig
iron, with the addition of only small quantities of scrap steel and
iron. At Le Creuzot large quantities of wrought iron are melted in
the bath. This iron is puddled in modified rotating Danks furnaces
containing a charge of a ton each. The furnaces have a mid-rib
dividing the product into two balls of 10 cwt., which are shingled
under a 10-ton hammer. The iron is of exceptional purity, containing
less than 0.01 per cent. of phosphorus and sulphur. I should add that
the two rotating furnaces produce 50 tons of billets in twenty-four
hours.